How many subplots in a novel are acceptable?

In my Suspense/Thriller Writers’ group on Facebook, one author asked, “How many subplots in a book are acceptable?”

Most of the writers thought that one or two subplots was enough, but horror writer Rob M. Miller gave a wonderful response that I’m reposting here. Considering the ephemeral nature of Facebook, in a couple of days his comment would have disappeared into the great maw of FB, and I didn’t want it to be lost forever. Rob said:

A broad question begging for a broad answer, of which there is only one that’s truly honest, even if horribly vague:

As many as the author can competently handle.

In the hands of a master, there can be many subplots, even into the double and triple digits, as can be read in the incredible work Shogun by James Clavell, or The Hobbit by Tolkien.

But to have a masterful work, there doesn’t have to be…